£20m price tag sees Stubbs race to head of Old Masters' field

George Stubbs's Gimcrack on Newmarket Heath, with a Trainer, a Stable-Lad, and a Jockey, depicting one of the most popular racehorses of the 18th century, goes up for auction this summer.

In British master George Stubbs's 1765 painting of the legendary English thoroughbred Gimcrack, the artist shows the horse several lengths ahead of its competitors. Now the work is expected to gallop into the record books to become one of the most expensive British paintings ever sold.

The work, Gimcrack on Newmarket Heath is set to fetch more than £20m when it is sold at Christie's in London in July. "Gimcrack was one of the most popular racehorses of the 18th century and was unusually small, but with incredible staying power," said Christie's senior director of British pictures John Stainton.

"He became something of a favourite, winning 28 out of 36 races which he was entered for, which was a remarkable feat."

The sale will make the work one of the most expensive Old Masters ever sold at auction. The current record for an Old Master is held by Flemish artist Sir Peter Paul Rubens, whose The Massacre of the Innocents sold for £50m in July 2002. If the Stubbs raises more than £20m it will make it the sixth most expensive Old Master ever sold, above Rembrandt's Portrait of a Lady Aged 62, which sold at Christie's for £20m in 2000.

"It is of great importance on many levels," said Mr Stainton. "The use of space is daring and unprecedented in British art at the time. It was a wonderfully wide panorama of the scene, and was unusual in that the central focus is shifted to the extreme left of the composition. In both pictorial and compositional senses it is groundbreaking."